The field of application and intended use of the invention lies in controlling an automated clutch, including, for example, a dual clutch, as well as a transmission, wherein, depending on a modeled temperature—which may also be found by calculation on the basis of a model of the clutch, for example—protective strategies are activated, which for example counteract warming or excessive wear. Relevant temperature models are, in particular, clutch temperature models, but also transmission temperature models.
Temperature models such as are disclosed, for example, in DE 10 2005 061 080 A1 or DE 10 2005 029 566 A1 are not dependent on the driving altitude above mean sea level or above standard elevation zero (the German standard for sea level). Temperature models for the clutch are known which take into account the interaction of friction and cooling capacity, as are temperature models for the transmission, in particular for the transmission fluid, which take into account the interaction of transmission efficiency and transmission cooling. Cooling is usually modeled empirically as a function of a variable that indicates the strength of the cooling air stream, for example as a function of vehicle velocity or of a speed of rotation.
The protective strategies are not effective in a timely manner at altitude, which can damage or even destroy the hardware. Alternatively, the protective strategies are developed for the “worst case” scenario; that is, as a result however at a low altitude the driving function is restricted disproportionately early by protective strategies, which the driver notices as a product deficiency in terms of performance, availability, unnecessary warnings or service alerts.
It has been recognized that altitude has a noticeable influence of up to 30 percent on cooling properties, because of the air density. The cooling of the clutch or transmission occurs by convection, i.e., by the “evacuation” of warmed air at the heated location to a cooler location, or completely out of the vehicle. One of the factors relevant for this is the air density, since it describes the “absorption capacity” for heat by the air. A lower air density results in a lower air volume or air mass flow, so that less heat can be removed by convection.